The present invention relates to a one-way roller clutch which is configured to transmit the rotation of its input member in one direction to its output member and stop transmission of the rotation of the input member when the output member begins to rotate at a higher speed than the input member.
This type of one-way clutch is disclosed in JP Patent Publication 60-57020A, which includes an outer ring having on its inner periphery a plurality of cam surfaces circumferentially spaced from each other at equal intervals, and an inner ring having an outer cylindrical surface. A wedge-shaped space is defined between each cam surface and the cylindrical surface. A retainer is mounted between the inner and outer rings and fixed to the outer ring. The retainer is formed with pockets each opposing one of the cam surfaces and each receiving a roller and an elastic member biasing the roller toward the narrow end of the wedge-shaped space. With this arrangement, when the inner and outer rings rotate relative to each other, they are selectively engaged and disengaged.
In order to stably press the cylindrical outer periphery of each roller, the elastic members of this one-way clutch comprise leaf springs each bent in a zigzag manner. Such elastic members tend to be broken due to stress concentration on the U-shaped bent portions thereof, and thus they are not sufficiently durable.
One effective way to avoid this problem would be to use coil springs as the elastic members. But due to limited installation space, it is impossible to use coil springs having a larger diameter than the rollers. Also, because each coil spring is brought into contact with the roller at two points, the attitudes of the coil springs tend to be unstable. In particular, if coil springs having a relatively small diameter are used, as shown in FIG. 7, the end of each coil spring 14 that is pressed against the roller 13 tends to slip along the cylindrical outer surface 13a of the roller 13, so that the spring is bent. In this state, the end of the spring separates from the roller as shown, so that the springs cannot apply a necessary load to the respective rollers 13. In the worst case, one or more of the springs may become trapped between the cylindrical outer surface 13a of the roller 13 and the cam surface 12 of the outer ring 11, and broken.
An object of the present invention is to provide a one-way roller clutch which uses coil springs for the elastic members for pressing the rollers, and of which the coil springs are sufficiently durable and can stably maintain their attitudes.